Semiconductor laser diodes are being used more widely in various types of optical communication systems because of their small size and relatively lower operating power as compared to other types of lasers. In such systems it is necessary to connect the laser diode to circuits formed of other electrical components, such as FETs, to properly operate the laser diode. In order to reduce the size of the system and to reduce the number of interconnections between the laser diode and the electrical components forming the circuit, it is desirable to form the laser diode and the electrical components as a monolithic integrated circuit. However, forming such an integrated circuit has several problems.
It is desirable that the integrated circuit be planar, i.e. have a planar surface, so as to facilitate forming the metallization pattern which connects the laser diode and the other electrical components on the surface of the device. In addition, laser diodes are generally formed of Group III-V materials so that it is necessary to form the integrated circuit and the other electrical components of the circuit of such materials. Of the Group III-V materials, GaAs is the most satisfactory material for forming FETs which have good operating characteristics. Therefore, the laser diode should be formed of Group III-V materials which are compatible with GaAs so that it can be satisfactorily formed on a substrate along with GaAs. However, in forming a laser diode and an FET in a monolithic body, it is necessary to isolate the FET and the laser diode both electrically and optically so that neither component interferes with the proper operation of the other.